1. Field of the Invention
This invention relates to a process and composition for acidizing an oil and gas well. More specifically, the invention relates to an aqueous micellar acidizing solution containing a high molecular weight alcohol and a phosphate ester surfactant.
2. Description of the Prior Art
The general concept of acidizing oil and gas wells has long been practiced commercially to clean up, stimulate, and to promote hydrocarbon production. Thus the injection of an aqueous solution of an acid such as hydrochloric, hydrofluoric, acetic, or the like is a common practice. Mutual solvents such as alcohols and ethylene glycol monobutyl ether are commonly added to well stimulation acids to enhance solids wetting, lower interfacial tension between acid and oil and to break down emulsion sludges. One particularly useful mixture is isopropyl alcohol and isooctyl alcohol such as described in U.S. Pat. No. 3,819,520 wherein isopropyl alcohol acts as a necessary cosolvent to render the isooctyl soluble and wherein the combination must be used at relatively high concentrations to be effective.
Surface active agents such as oxyalkylated polyols or oxyalkylated alkyl phenols with sulfated oxyalkylated alcohols and glycol ethers are known to be used in acids as are oxyalkylated alcohols and alkyl sulfonate in butyl alcohol for many of the above purposes. Other types of surfactants such as the ethylene oxide adduct of octyl alcohol or nonyl phenols have been used.
However, none of the above are as effective as is desired. The glycol ethers, mixed alcohols, and the like are not as good as the surfactants in wetting oily solids, dispersing solids, or lowering surface and interfacial tension. And, surfactants often form (stabilize) harmful emulsions and are not as effective in promoting oil/acid miscibility as are the higher alcohols, which have very low solubility in aqueous acid solutions.